Sheets of cardboard mat, glass and other materials are frequently cut to provide components having openings and/or perimeters of circular or elliptical (generally referred to in the trade as "oval") configuration. Such components are widely used for mounting and framing of pictures and the like.
Machines are known in the art, and are commercially available, for cutting planar workpieces to such shapes. Exemplary are the devices described in Pierce U.S. Pat. No. 4,112,793, issued Sep. 12, 1978, and in Kozyrski et al U.S. Pat. No. 5,099,727, issued Mar. 31, 1992, both of which employ mechanisms that implement the so-called "Scottish yoke" principle by having the functional components (e.g., the cutting head) operatively mounted on a rotating member that is constrained to reciprocate on two perpendicular axes. Hand-held scribing, drafting and cutting devices incorporating such mechanisms are also known in the art and are commercially available, as shown for example in Ruger U.S. Pat. No. 2,458,208, issued Jan. 4, 1949; Scott U.S. Pat. No. 2,595,417, issued May 6, 1952; Shaw U.S. Pat. No. 2,762,126, issued Sep. 11, 1956; and Pierce U.S. Pat. No. 4,244,106, issued January 1981.
Machines and devices of the character described are generally capable of defining circular, as well as elliptical, shapes, the generation of a circle merely being a matter of setting a zero differential (or offset) between major and minor axis lengths. A serious drawback in DIY (do-it-yourself) apparatus of this kind, made available heretofore, resides in this aspect; i.e., in the difficulty entailed in reconfiguring the device between its circle- and ellipse-defining modes of operation.